In the tomb of Seti I, a brilliantly decorated underground mansion for the soul of a Pharaoh dead 3,000 years, tourists pay little attention to the pit in the floor or the shaft that leads down from it into darkness.

Bits of Kleenex and cigarette butts mingle in the dust at the narrow opening to the tunnel. It is neglected in every way and it is easy to assume that it leads to something no one cares to see. After all, the tomb of Seti I in the Valley of the Kings was first excavated in 1802. In all the years since, one would think its every secret had been revealed.

In fact, no man alive knows where the tunnel leads.

"Tomb robbers presume that it went down to the real burial chambers; that the first burial chamber was probably a decoy, a fake," said Kent Weeks, an Egyptologist from the University of California at Berkeley. "It's entirely possible."

Like many of ancient Egypt's historical sites, the tunnel leading down from Seti I's tomb is a mystery lying exposed, discovered but unexplored, its riches imagined, but uninvestigated.

They are left untouched partly because what scholars and scientists call the "new archeology" has grown so sophisticated.

Egyptologists are interested in such minute detail whenever they start to dig that everything down to the pollen and the fleas discovered in the dust has to be analyzed by specialists -- in chemistry, conservation, surveying, biology, paleobotany.

"Most people, when they think about archeology, they think about objects," said Michael Jones, who works with the American Research Center in Egypt. "But archeology is really about people."

Bones found in ancient trash heaps, for instance, have shown that in the time of the Pharaohs many people ate pork, even though pigs are nowhere to be seen in the carvings and monuments of the period. The pollen samples indicate what crops were grown.

"You find that what is written up in the tombs is not necessarily what they did in the villages," said Jones.

But the expense of employing the necessary specialists makes excavation prohibitive. Then to publish the findings in exhaustive scientific detail costs still more.

"The days of finding enough gold and jewels to sell to finance part of your venture disappeared 100 years ago," said Weeks. Today, laws governing antiquities would keep them from being sold legally even if they were found.

Having seen the ravages wrought by clumsy excavations in the past, modern archeologists have nightmares about depriving, through their own ineptitude or lack of technology, the scientists of the future.

"Archeology is a process of destruction," said Jones. "Once you dig up the ancient remains, you start to destroy them, and if you don't do it properly they're gone for good."

Then, too, there is the awesome scope of the historical riches at hand.

At Giza, around the pyramids that have attracted tourists for more than 23 centuries, there are hundreds of known tombs that archeologists have never opened.

Here, surrounded by the stark, sheer cliffs in the Valley of the Kings, 62 tombs have been discovered. The last of them, found in 1922, was the treasure trove of Tutankhamen. Yet Egyptologists, said Weeks, have only "scratched the surface" here.

"Of those 62 tombs, about half are accessible. That is, you can walk into them, look around the walls," said Weeks. "Of those tombs, fewer than half a dozen have been published" -- their every detail recorded in scholarly books -- "or completely cleared."

In some cases, discoveries are there to be made right under the feet of the thousands of tourists who troop through the tombs every month.

Last year, according to Weeks, an archeologist cleared away some gravel in the shallow pit beneath the sarcophagus of Rameses VI, which lies shattered and split in two by ancient robbers. The archeologist found bits of funerary furniture and figurines never discovered, said Weeks, even though Rameses VI's is one of the most visited tombs in the valley.

To discover and preserve what does exist, Weeks and other archeologists have been turning to methods borrowed from some unexpected places.

For two of his eight years here, Weeks flew around the upper reaches of the valley's cliffs in a hot-air balloon.

"We literally have been able to float along the edges of the cliff faces looking into all the nooks and crannies," he said.

When a potential opening is discovered, Weeks or his students rappel down to it. Rock climbing, as Weeks noted, is a popular pastime with some of his California graduate students.

More recently, Weeks' Berkeley-Theban Mapping Project has been using radar and other apparatus designed by the U.S. Bureau of Mines to find mine shafts.

"Two hundred years ago there were five tombs visible in the valley that are not visible today. They've been lost," said Weeks. The idea is to discover which tombs may be endangered by development in the area: by irrigation or rising ground water, or by building projects.

"It used to be said that the safest antiquities in the world are the ones that have not been dug. That isn't true anymore," said Weeks, "because the ones underground are also being threatened -- in some instances as badly threatened as those that have been excavated."

So far, Weeks believes he has located one of the five lost tombs. "I suspect the entrance to it lies immediately next to the septic tank of the rest house."

Even with all the technology, meticulousness and caution of the new archeology, however, there seems to be a little bit of Indiana Jones left among many of the Egyptologists. And the tunnel at the end of the tomb of Seti I seems to bring it out.

The Italian archeologist who discovered it in 1802 was 6 feet 8 inches tall and weighed 300 pounds. He was only able to squeeze about 300 feet down it before stopping. An Egyptian team made it about 525 feet, and five years ago Weeks tried slithering to its end, but made it no farther than the Egyptians had.

"On one occasion we found several 100-pound blocks had fallen in from the ceiling" onto the rope they were using to pull themselves in and out of the tunnel, he said. They had to crawl out, very carefully, around them. "We still don't know what lies at the bottom or how much farther it goes."

Sonar, radar and electrical resistivity tests may at last find the answer. "We can go over the area and determine if there are any voids or irregularities underground," said Weeks.

But to know for certain what the voids mean, you would have to dig. Weeks suggested that the risks, both to the archeologists and to the tomb, remain so great for the present that solving the mystery of Seti I's tomb may well have to wait for generations of archeologists.